igneous
Granite Pebbles
Granite (composed primarily of Quartz SiO2, Feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8), and Mica)
Hardness: 6-7 on Mohs scale; Color: Mottled salt-and-pepper (white, grey, black); Luster: Phaneritic (crystalline) texture with vitreous luster on individual crystals; Crystal structure: Granular/Crystalline; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled salt-and-pepper (white, grey, black)
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled salt-and-pepper (white, grey, black); Luster: Phaneritic (crystalline) texture with vitreous luster on individual crystals; Crystal structure: Granular/Crystalline; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow cooling and crystallization of silica-rich magma deep underground (plutonic). These specific rounded specimens shaped by fluvial or glacial erosion over thousands to millions of years.
Uses & applications
Used in landscaping, construction aggregate, decorative river rock, and used for polishing in rock tumblers for hobbyists.
Geological facts
Granite is the primary rock component of the Earth's continental crust. Because it is so hard and durable, it can travel long distances in rivers without breaking apart, which is why smooth granite pebbles are common in riverbeds.
Field identification & locations
Identify by the visible grains of quartz (glassy), feldspar (opaque white/pink), and dark minerals like biotite. Often found in riverbeds, glacial deposits, and beaches. Collectors look for unique mineral banding or inclusions.
